ON THE MAINTENANCE OF ZONAL CIRCULATION IN THE ATMOSPHERE

Abstract

The maintenance of a jet-type zonal circulation is discussed from the viewpoint of vorticity balance. Through skin friction, the atmosphere gains vorticity from the earth in the region of anticyclonic vorticity at the surface, and returns it to the earth in the region of cyclonic vorticity at the surface. There are two processes to carry out the vorticity transfer from low to high latitudes: meridional circulation and large, horizontal vortical systems. The efficiency of the two in compensating the frictional effect is about the same in low latitudes. In middle latitudes, the large, horizontal vortical systems are far more efficient. In high latitudes, the role of the mean circulation in maintaining the zonal circulation is negligible.